[WIP] Add head and tail cli options

[anusha5695]

Issue:
This PR is related to the issue : #16

Summary of changes:

1. Add arguments in the allowed list (--head and --tail)
2. Read arguments from keyworded args
3. If either head or tail is present, then query the Events using (first() for head and .order_by(desc()).first()
4. Else use the .all()

[anusha5695]

@vinayak-mehta : Could you please review this?

[vinayak-mehta]

Yes! Please give me one day.

[anusha5695]

@vinayak-mehta : Hi any updates on this

[vinayak-mehta]

Looks like there are merged conflicts. Two changes are needed:

1. Both options should be mutually exclusive
2. There should be an option to specify number of lines for each. For example:

• conrad show --head 5: To show first 5 rows
• conrad show --tail 5: To show last 5 rows

You can try using the head and tail unix commands to get a sense of how they work.

[anusha5695]

@vinayak-mehta sure will make the changes